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<meta name="description" content="Lua 面向对象  面向对象编程（Object Oriented Programming，OOP）是一种非常流行的计算机编程架构。   以下几种编程语言都支持面向对象编程：   C++ Java Objective-C Smalltalk C# Ruby  面向对象特征  1） 封装：指能够把一个实体的信息、功能、响应都装入一个单独的对象中的特性。 2） 继承：继承的方法允许在不改动原程序的基础上对其进行扩充，这样使得原功能得以保存，而..">
		
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			<h1>Lua 面向对象</h1>
<p>
面向对象编程（Object Oriented Programming，OOP）是一种非常流行的计算机编程架构。</p>
<p>
 以下几种编程语言都支持面向对象编程：</p>
</p>
<ul>
<li>C++</li>
<li>Java</li>
<li>Objective-C</li>
<li>Smalltalk</li>
<li>C#</li>
<li>Ruby</li>
</ul><hr>
<h2>面向对象特征</h2>
<ul>
<li>1） 封装：指能够把一个实体的信息、功能、响应都装入一个单独的对象中的特性。</li><li>
2） 继承：继承的方法允许在不改动原程序的基础上对其进行扩充，这样使得原功能得以保存，而新功能也得以扩展。这有利于减少重复编码，提高软件的开发效率。</li><li>
3） 多态：同一操作作用于不同的对象，可以有不同的解释，产生不同的执行结果。在运行时，可以通过指向基类的指针，来调用实现派生类中的方法。</li><li>
4）抽象：抽象(Abstraction)是简化复杂的现实问题的途径，它可以为具体问题找到最恰当的类定义，并且可以在最恰当的继承级别解释问题。</li></ul>
<hr>
<h2>Lua 中面向对象</h2>
<p>
我们知道，对象由属性和方法组成。LUA中最基本的结构是table，所以需要用table来描述对象的属性。</p>
<p>lua 中的 function 可以用来表示方法。那么LUA中的类可以通过 table + function 模拟出来。</p><p>至于继承，可以通过 metetable 模拟出来（不推荐用，只模拟最基本的对象大部分实现够用了）。</p>
</p>
<p>Lua 中的表不仅在某种意义上是一种对象。像对象一样，表也有状态（成员变量）；也有与对象的值独立的本性，特别是拥有两个不同值的对象（table）代表两个不同的对象；一个对象在不同的时候也可以有不同的值，但他始终是一个对象；与对象类似，表的生命周期与其由什么创建、在哪创建没有关系。对象有他们的成员函数，表也有：
</p>

<div class="example"> <div class="example_code">
Account <span style="color: #Gray;">=</span> <span style="color: Olive;">&#123;</span>balance <span style="color: #Gray;">=</span> <span style="color: Maroon;">0</span><span style="color: Olive;">&#125;</span><br />
<span style="color: Green; font-weight: bold;">function</span> Account<span style="color: #Gray;">.</span>withdraw <span style="color: Olive;">&#40;</span>v<span style="color: Olive;">&#41;</span><br />
&nbsp; &nbsp; Account<span style="color: #Gray;">.</span>balance <span style="color: #Gray;">=</span> Account<span style="color: #Gray;">.</span>balance <span style="color: #Gray;">-</span> v<br />
<span style="color: Green; font-weight: bold;">end</span><br />
</div></div>

<p>
这个定义创建了一个新的函数，并且保存在Account对象的withdraw域内，下面我们可以这样调用：</p>
<pre>
Account.withdraw(100.00)
</pre>
<h3>一个简单实例</h3>
<p>以下简单的类包含了三个属性： area, length 和 breadth，printArea方法用于打印计算结果：</p>

<div class="example"><h2 class="example">实例</h2> <div class="example_code">
<span style="color: #a50; font-style: italic;">-- 元类</span><br />
Rectangle <span style="color: #Gray;">=</span> <span style="color: Olive;">&#123;</span>area <span style="color: #Gray;">=</span> <span style="color: Maroon;">0</span><span style="color: #Gray;">,</span> length <span style="color: #Gray;">=</span> <span style="color: Maroon;">0</span><span style="color: #Gray;">,</span> breadth <span style="color: #Gray;">=</span> <span style="color: Maroon;">0</span><span style="color: Olive;">&#125;</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 派生类的方法 new</span><br />
<span style="color: Green; font-weight: bold;">function</span> Rectangle<span style="color: #Gray;">:</span>new <span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>length<span style="color: #Gray;">,</span>breadth<span style="color: Olive;">&#41;</span><br />
&nbsp; o <span style="color: #Gray;">=</span> o <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Olive;">&#123;</span><span style="color: Olive;">&#125;</span><br />
&nbsp; <span style="color: #05a;">setmetatable</span><span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span> self<span style="color: Olive;">&#41;</span><br />
&nbsp; self<span style="color: #Gray;">.</span>__index <span style="color: #Gray;">=</span> self<br />
&nbsp; self<span style="color: #Gray;">.</span>length <span style="color: #Gray;">=</span> length <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Maroon;">0</span><br />
&nbsp; self<span style="color: #Gray;">.</span>breadth <span style="color: #Gray;">=</span> breadth <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Maroon;">0</span><br />
&nbsp; self<span style="color: #Gray;">.</span>area <span style="color: #Gray;">=</span> length<span style="color: #Gray;">*</span>breadth<span style="color: #Gray;">;</span><br />
&nbsp; <span style="color: Green; font-weight: bold;">return</span> o<br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 派生类的方法 printArea</span><br />
<span style="color: Green; font-weight: bold;">function</span> Rectangle<span style="color: #Gray;">:</span>printArea <span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;矩形面积为 &quot;</span><span style="color: #Gray;">,</span>self<span style="color: #Gray;">.</span>area<span style="color: Olive;">&#41;</span><br />
<span style="color: Green; font-weight: bold;">end</span><br />
</div></div>

<h3>创建对象</h3>
<p>创建对象是为类的实例分配内存的过程。每个类都有属于自己的内存并共享公共数据。</p>
<pre>
r = Rectangle:new(nil,10,20)
</pre>
<h3>访问属性</h3>
<p>我们可以使用点号(.)来访问类的属性：</p>
<pre>
print(r.length)
</pre>
<h3>访问成员函数</h3>
<p>我们可以使用冒号 <span class="marked">:</span> 来访问类的成员函数：</p>
<pre>
r:printArea()
</pre>
<p>内存在对象初始化时分配。</p>

<h3>完整实例</h3>
<p>以下我们演示了 Lua 面向对象的完整实例：</p>

<div class="example"><h2 class="example">实例</h2> <div class="example_code">
<span style="color: #a50; font-style: italic;">-- 元类</span><br />
Shape <span style="color: #Gray;">=</span> <span style="color: Olive;">&#123;</span>area <span style="color: #Gray;">=</span> <span style="color: Maroon;">0</span><span style="color: Olive;">&#125;</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 基础类方法 new</span><br />
<span style="color: Green; font-weight: bold;">function</span> Shape<span style="color: #Gray;">:</span>new <span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>side<span style="color: Olive;">&#41;</span><br />
&nbsp; o <span style="color: #Gray;">=</span> o <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Olive;">&#123;</span><span style="color: Olive;">&#125;</span><br />
&nbsp; <span style="color: #05a;">setmetatable</span><span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span> self<span style="color: Olive;">&#41;</span><br />
&nbsp; self<span style="color: #Gray;">.</span>__index <span style="color: #Gray;">=</span> self<br />
&nbsp; side <span style="color: #Gray;">=</span> side <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Maroon;">0</span><br />
&nbsp; self<span style="color: #Gray;">.</span>area <span style="color: #Gray;">=</span> side<span style="color: #Gray;">*</span>side<span style="color: #Gray;">;</span><br />
&nbsp; <span style="color: Green; font-weight: bold;">return</span> o<br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 基础类方法 printArea</span><br />
<span style="color: Green; font-weight: bold;">function</span> Shape<span style="color: #Gray;">:</span>printArea <span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;面积为 &quot;</span><span style="color: #Gray;">,</span>self<span style="color: #Gray;">.</span>area<span style="color: Olive;">&#41;</span><br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 创建对象</span><br />
myshape <span style="color: #Gray;">=</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span><span style="color: Navy;">nil</span><span style="color: #Gray;">,</span><span style="color: Maroon;">10</span><span style="color: Olive;">&#41;</span><br />
<br />
myshape<span style="color: #Gray;">:</span>printArea<span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
</div></div>

<p>执行以上程序，输出结果为：</p>
<pre>
面积为 &nbsp;&nbsp;&nbsp;&nbsp;100
</pre>
<hr>
<h2>Lua 继承</h2>
<p>继承是指一个对象直接使用另一对象的属性和方法。可用于扩展基础类的属性和方法。</p>
<p>以下演示了一个简单的继承实例：</p>

<div class="example"><div class="example_code">
<span style="color: #a50; font-style: italic;">-- Meta class</span><br />
Shape <span style="color: #Gray;">=</span> <span style="color: Olive;">&#123;</span>area <span style="color: #Gray;">=</span> <span style="color: Maroon;">0</span><span style="color: Olive;">&#125;</span><br />
<span style="color: #a50; font-style: italic;">-- 基础类方法 new</span><br />
<span style="color: Green; font-weight: bold;">function</span> Shape<span style="color: #Gray;">:</span>new <span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>side<span style="color: Olive;">&#41;</span><br />
&nbsp; o <span style="color: #Gray;">=</span> o <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Olive;">&#123;</span><span style="color: Olive;">&#125;</span><br />
&nbsp; <span style="color: #05a;">setmetatable</span><span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span> self<span style="color: Olive;">&#41;</span><br />
&nbsp; self<span style="color: #Gray;">.</span>__index <span style="color: #Gray;">=</span> self<br />
&nbsp; side <span style="color: #Gray;">=</span> side <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Maroon;">0</span><br />
&nbsp; self<span style="color: #Gray;">.</span>area <span style="color: #Gray;">=</span> side<span style="color: #Gray;">*</span>side<span style="color: #Gray;">;</span><br />
&nbsp; <span style="color: Green; font-weight: bold;">return</span> o<br />
<span style="color: Green; font-weight: bold;">end</span><br />
<span style="color: #a50; font-style: italic;">-- 基础类方法 printArea</span><br />
<span style="color: Green; font-weight: bold;">function</span> Shape<span style="color: #Gray;">:</span>printArea <span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;面积为 &quot;</span><span style="color: #Gray;">,</span>self<span style="color: #Gray;">.</span>area<span style="color: Olive;">&#41;</span><br />
<span style="color: Green; font-weight: bold;">end</span><br />
</div></div>

<p>接下来的实例，Square 对象继承了 Shape 类:</p>

<div class="example"><div class="example_code">
Square <span style="color: #Gray;">=</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
<span style="color: #a50; font-style: italic;">-- Derived class method new</span><br />
<span style="color: Green; font-weight: bold;">function</span> Square<span style="color: #Gray;">:</span>new <span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>side<span style="color: Olive;">&#41;</span><br />
&nbsp; o <span style="color: #Gray;">=</span> o <span style="color: Teal; font-weight: bold;">or</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>side<span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">setmetatable</span><span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span> self<span style="color: Olive;">&#41;</span><br />
&nbsp; self<span style="color: #Gray;">.</span>__index <span style="color: #Gray;">=</span> self<br />
&nbsp; <span style="color: Green; font-weight: bold;">return</span> o<br />
<span style="color: Green; font-weight: bold;">end</span><br />
</div></div>

<h3>完整实例</h3>
<p>以下实例我们继承了一个简单的类，来扩展派生类的方法，派生类中保留了继承类的成员变量和方法：</p>

<div class="example"><h2 class="example">实例</h2> <div class="example_code">
<span style="color: #a50; font-style: italic;">-- Meta class</span><br />
Shape <span style="color: #Gray;">=</span> <span style="color: Olive;">&#123;</span>area <span style="color: #Gray;">=</span> <span style="color: Maroon;">0</span><span style="color: Olive;">&#125;</span><br />
<span style="color: #a50; font-style: italic;">-- 基础类方法 new</span><br />
<span style="color: Green; font-weight: bold;">function</span> Shape<span style="color: #Gray;">:</span>new <span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>side<span style="color: Olive;">&#41;</span><br />
&nbsp; o <span style="color: #Gray;">=</span> o <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Olive;">&#123;</span><span style="color: Olive;">&#125;</span><br />
&nbsp; <span style="color: #05a;">setmetatable</span><span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span> self<span style="color: Olive;">&#41;</span><br />
&nbsp; self<span style="color: #Gray;">.</span>__index <span style="color: #Gray;">=</span> self<br />
&nbsp; side <span style="color: #Gray;">=</span> side <span style="color: Teal; font-weight: bold;">or</span> <span style="color: Maroon;">0</span><br />
&nbsp; self<span style="color: #Gray;">.</span>area <span style="color: #Gray;">=</span> side<span style="color: #Gray;">*</span>side<span style="color: #Gray;">;</span><br />
&nbsp; <span style="color: Green; font-weight: bold;">return</span> o<br />
<span style="color: Green; font-weight: bold;">end</span><br />
<span style="color: #a50; font-style: italic;">-- 基础类方法 printArea</span><br />
<span style="color: Green; font-weight: bold;">function</span> Shape<span style="color: #Gray;">:</span>printArea <span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;面积为 &quot;</span><span style="color: #Gray;">,</span>self<span style="color: #Gray;">.</span>area<span style="color: Olive;">&#41;</span><br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 创建对象</span><br />
myshape <span style="color: #Gray;">=</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span><span style="color: Navy;">nil</span><span style="color: #Gray;">,</span><span style="color: Maroon;">10</span><span style="color: Olive;">&#41;</span><br />
myshape<span style="color: #Gray;">:</span>printArea<span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
<br />
Square <span style="color: #Gray;">=</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
<span style="color: #a50; font-style: italic;">-- 派生类方法 new</span><br />
<span style="color: Green; font-weight: bold;">function</span> Square<span style="color: #Gray;">:</span>new <span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>side<span style="color: Olive;">&#41;</span><br />
&nbsp; o <span style="color: #Gray;">=</span> o <span style="color: Teal; font-weight: bold;">or</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>side<span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">setmetatable</span><span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span> self<span style="color: Olive;">&#41;</span><br />
&nbsp; self<span style="color: #Gray;">.</span>__index <span style="color: #Gray;">=</span> self<br />
&nbsp; <span style="color: Green; font-weight: bold;">return</span> o<br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 派生类方法 printArea</span><br />
<span style="color: Green; font-weight: bold;">function</span> Square<span style="color: #Gray;">:</span>printArea <span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;正方形面积为 &quot;</span><span style="color: #Gray;">,</span>self<span style="color: #Gray;">.</span>area<span style="color: Olive;">&#41;</span><br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 创建对象</span><br />
mysquare <span style="color: #Gray;">=</span> Square<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span><span style="color: Navy;">nil</span><span style="color: #Gray;">,</span><span style="color: Maroon;">10</span><span style="color: Olive;">&#41;</span><br />
mysquare<span style="color: #Gray;">:</span>printArea<span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
<br />
Rectangle <span style="color: #Gray;">=</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
<span style="color: #a50; font-style: italic;">-- 派生类方法 new</span><br />
<span style="color: Green; font-weight: bold;">function</span> Rectangle<span style="color: #Gray;">:</span>new <span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span>length<span style="color: #Gray;">,</span>breadth<span style="color: Olive;">&#41;</span><br />
&nbsp; o <span style="color: #Gray;">=</span> o <span style="color: Teal; font-weight: bold;">or</span> Shape<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span>o<span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">setmetatable</span><span style="color: Olive;">&#40;</span>o<span style="color: #Gray;">,</span> self<span style="color: Olive;">&#41;</span><br />
&nbsp; self<span style="color: #Gray;">.</span>__index <span style="color: #Gray;">=</span> self<br />
&nbsp; self<span style="color: #Gray;">.</span>area <span style="color: #Gray;">=</span> length <span style="color: #Gray;">*</span> breadth<br />
&nbsp; <span style="color: Green; font-weight: bold;">return</span> o<br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 派生类方法 printArea</span><br />
<span style="color: Green; font-weight: bold;">function</span> Rectangle<span style="color: #Gray;">:</span>printArea <span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;矩形面积为 &quot;</span><span style="color: #Gray;">,</span>self<span style="color: #Gray;">.</span>area<span style="color: Olive;">&#41;</span><br />
<span style="color: Green; font-weight: bold;">end</span><br />
<br />
<span style="color: #a50; font-style: italic;">-- 创建对象</span><br />
myrectangle <span style="color: #Gray;">=</span> Rectangle<span style="color: #Gray;">:</span>new<span style="color: Olive;">&#40;</span><span style="color: Navy;">nil</span><span style="color: #Gray;">,</span><span style="color: Maroon;">10</span><span style="color: #Gray;">,</span><span style="color: Maroon;">20</span><span style="color: Olive;">&#41;</span><br />
myrectangle<span style="color: #Gray;">:</span>printArea<span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
</div></div>

<p>执行以上代码，输出结果为：</p>

<pre>
面积为 &nbsp;&nbsp;&nbsp;&nbsp;100
正方形面积为 &nbsp;&nbsp;&nbsp;&nbsp;100
矩形面积为 &nbsp;&nbsp;&nbsp;&nbsp;200
</pre>

<hr><h2>函数重写</h2>
<p>Lua 中我们可以重写基础类的函数，在派生类中定义自己的实现方式：</p>

<div class="example"><div class="example_code">
<span style="color: #a50; font-style: italic;">-- 派生类方法 printArea</span><br />
<span style="color: Green; font-weight: bold;">function</span> Square<span style="color: #Gray;">:</span>printArea <span style="color: Olive;">&#40;</span><span style="color: Olive;">&#41;</span><br />
&nbsp; <span style="color: #05a;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;正方形面积 &quot;</span><span style="color: #Gray;">,</span>self<span style="color: #Gray;">.</span>area<span style="color: Olive;">&#41;</span><br />
<span style="color: Green; font-weight: bold;">end</span><br />
</div></div>

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<div id="postcomments"  style="display:none;" >
	<ol class="commentlist">
		<li class="comment even thread-even depth-1" id="comment-20159"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;达也酱</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;jja***@163.com</p></div><div id="runoobvote-id-20159" data-commid = "20159" class="upvotejs"><a class="upvote"></a> <span class="count">45</span></div></div><div class="comt-main" id="div-comment-20159"><p>按实例的写法，每次new新实例的时候都需要将第一个变量的值设为nil,很不方便。</p>

<p>可以稍做变形，把变量o放在函数里创建，免去麻烦。</p>

<pre>--创建一个类，表示四边形
local RectAngle = { length, width, area} --声明类名和类成员变量

     function RectAngle: new (len,wid) --声明新建实例的New方法
        local o = {
        --设定各个项的值
         length = len or 0,
         width = wid or 0,
         area =len*wid
        }
        setmetatable(o,{__index = self} )--将自身的表映射到新new出来的表中
        return o
    end
    
    function RectAngle:getInfo()--获取表内信息的方法
        return self.length,self.width,self.area
    end


a = RectAngle:new(10,20)
print(a:getInfo())      -- 输出：10    20    200
b = RectAngle:new(10,10)
print(b:getInfo())      -- 输出：10    10    100
print(a:getInfo())      -- 输出：10    20    200</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">达也酱</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;达也酱</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;jja***@163.com</p></div></span>6年前 (2017-11-10)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-26177"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;gray.yang</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;gra***ang@fibocom.com</p></div><div id="runoobvote-id-26177" data-commid = "26177" class="upvotejs"><a class="upvote"></a> <span class="count">24</span></div></div><div class="comt-main" id="div-comment-26177"><p>补充： <span class="marked">.</span> 与 <span class="marked">:</span> 的区别在于使用 <span class="marked">:</span> 定义的函数隐含 <strong>self</strong> 参数，使用 <span class="marked">:</span> 调用函数会自动传入 <strong>table</strong> 至 <strong>self</strong> 参数，示例：</p>

<pre>classA={}
function classA:getob(name)
    print(self)
    ob={}
    setmetatable(ob,self)
    self.__index=self
    self.name=name
    return ob
end

function classA:getself()
    return self
end

c1=classA:getob("A")
c2=classA:getob("B")
print(string.rep("*",30))
print(c1:getself())
print(c2:getself())
print(string.rep("*",30))

----------------------继承------------------------

classB=classA:getob()    ----非常重要，用于获取继承的self
function classB:getob(name,address)
    ob=classA:getob(name)
    setmetatable(ob,self)
    self.__index=self
    self.address=address
    return ob
end

c3=classB:getob("gray.yang","shenzhen")
print(c3:getself())</pre>
<p>输出结果：</p>
<pre>
table: 0x7fc99d404c80
table: 0x7fc99d404c80
******************************
table: 0x7fc99d402c50
table: 0x7fc99d404cc0
******************************
table: 0x7fc99d404c80
table: 0x7fc99d404c80
table: 0x7fc99d405640</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">gray.yang</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;gray.yang</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;gra***ang@fibocom.com</p></div></span>5年前 (2018-04-11)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-28845"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;miaosu5cm</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;mia***5cm@163.com</p></div><div id="runoobvote-id-28845" data-commid = "28845" class="upvotejs"><a class="upvote"></a> <span class="count">6</span></div></div><div class="comt-main" id="div-comment-28845"><p><strong>模拟类和继承</strong></p>

<pre>classA={}

function classA.new(cls,...)     --定义类方法时使用"."号，不适用隐式传参
    this={}
    setmetatable(this,cls)
    cls.__index=cls           --将元表的__index设为自身，访问表的属性不存在时会搜索元表
    cls.init(this,...)        --初始化表，注意访问类的方法都是"."，此时不会隐式传入参数
    return this
end

function classA.init(self,name)
    self.name=name
end

function classA.getname(self)
    return self.name
end

p=classA:new("gray.yang")
print(p:getname())
print(string.rep("*",50))</pre>

<p><strong>模拟继承</strong></p>

<pre>classB=classA:new()        --获得实例

function classB.new(cls,...)
    this={}
    setmetatable(this,cls)
    cls.__index=cls
    cls.init(this,...)
    return this
end

function classB.init(self,name,address)
    super=getmetatable(self)
    super:init(name)                --使用父类初始化
    self.address=address
end

function classB.getaddress(self)
    return self.address
end

b=classB:new("tom.li","shenzhen")

print("getbname==============&gt;",b:getname())
print("getbaddress===========&gt;",b:getaddress())</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">miaosu5cm</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;miaosu5cm</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;mia***5cm@163.com</p></div></span>5年前 (2018-06-28)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-29634"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Ives</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;571***385@qq.com</p></div><div id="runoobvote-id-29634" data-commid = "29634" class="upvotejs"><a class="upvote"></a> <span class="count">2</span></div></div><div class="comt-main" id="div-comment-29634"><p><strong>多重继承</strong></p>

<pre>-- 在table 'plist'中查找'k'
local function search(k, plist)
  for i = 1, #plist do
    local v = plist[i][k]      -- 尝试第i个基类
    if v then return v end
  end
end

function createClass(...)
  local c = {}                   -- 新类
  local parents = {...}

  -- 类在其父类列表中的搜索方法
  setmetatable(c, {__index = function(t, k)
    return search(k, parents)
  end})

  -- 将'c'作为其实例的元表
  c.__index = c

  -- 为这个新类定义一个新的构造函数
  function c:new(o)
    o = o or {}
    setmetatable(o, c)
    return o
  end

  return c                       -- 返回新类
end

-- 类Named
Named = {}
function Named:getname()
  return self.name
end

function Named:setname(n)
  self.name = n
end

-- 类Account
Account = {balance = 0}
function Account:withdraw(w)
  self.balance = self.balance - v
end

-- 创建一个新类NamedAccount，同时从Account和Named派生
NamedAccount = createClass(Account, Named)

account = NamedAccount:new()
account:setname("Ives")
print(account:getname())         -- 输出 Ives</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">Ives</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Ives</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;571***385@qq.com</p></div></span>5年前 (2018-07-15)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-33783"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;大轩</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;tol***uan@163.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://blog.csdn.net/vermilliontear/article/details/50650883">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-33783" data-commid = "33783" class="upvotejs"><a class="upvote"></a> <span class="count">8</span></div></div><div class="comt-main" id="div-comment-33783"><p><strong>一个简单的面向对象实现</strong></p>

<pre>--[[
Lua 中使用":"实现面向对象方式的调用。":"只是语法糖，它同时在方法的声明与实现中增加了一个
名为 self 的隐藏参数，这个参数就是对象本身。
]]

--实例：
Account = {balance = 0};

--生成对象
function Account:new(o)
    o = o or {}; --如果用户没有提供对象，则创建一个。
    setmetatable(o, self); --将 Account 作为新创建的对象元表
    self.__index = self; --将新对象元表的 __index 指向为 Account（这样新对象就可以通过索引来访问 Account 的值了）
    
    return o; --将新对象返回
end

--存款
function Account:deposit(v)
    self.balance = self.balance + v;
end

--取款
function Account:withdraw(v)
    self.balance = self.balance - v;
end

--查询
function Account:demand()
    print(self.balance);
end

--创建对象
myAccount = Account:new();
--通过索引访问
print(myAccount.balance);
--调用函数
myAccount:deposit(100);
myAccount:withdraw(50);
myAccount:demand();</pre>

<p>执行结果：</p>
<pre>0
50
[Finished in 0.0s]</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">大轩</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;大轩</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;tol***uan@163.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://blog.csdn.net/vermilliontear/article/details/50650883">&nbsp;&nbsp;参考地址</a></p></div></span>5年前 (2018-08-08)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-40253"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;wildwolf</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;wil***lf12@qq.com</p></div><div id="runoobvote-id-40253" data-commid = "40253" class="upvotejs"><a class="upvote"></a> <span class="count">1</span></div></div><div class="comt-main" id="div-comment-40253"><p>其中 A 为抽象类，B 为矩形类，C 为立方体类。</p>
 
<p>C 继承 B，B 继承 A。</p>

<p>类对象各自独立，不影响类默认成员属性值。</p>

<pre>B = {length, width, area}

function B:new(len,wid)
    local A = {length=0,width=0}
    local o = {}
    setmetatable(o,A)
    B.__index=A
    o.length=len or A.length
    o.width=wid or A.width
    o.area=o.length*o.width
    return o
end

a=B:new(2,3)
b=B:new(3,4)
print("长方形a的面积为"..a.area)
print("长方形b的面积为"..b.area)
print("长方形a的面积仍然为"..a.area..", a与b独立存在")

c=B:new()
print("长方形c根据默认构造函数的面积为"..c.area..", c的长宽分别为",c.length,c.width)

--立方体C，继承长方形类B
C = {high=0, volume=0, rectangle=B.new()} --增加体积值和高度
C.__index=C        
function C:new(len, wid, hig)
    local o={}
    
    
    setmetatable(o,C)    --将原始类C作为它对象的原表
    
    o.rectangle=B:new(len,wid)
    o.high=hig or C.high
    o.volume=o.high*o.rectangle.area
    return o
end

cubeA=C:new(2,3,4)
cubeB=C:new(3,4,5)
print("立方体A的体积为"..cubeA.volume)
print("立方体B的体积为"..cubeB.volume)
print("立方体A的体积仍然为"..cubeA.volume..", A与B独立存在")

print("立方体A底面长方体的长与宽分别为"
    ,cubeA.rectangle.length
    ,cubeA.rectangle.width)
print("立方体B底面长方体的长与宽分别为"
    ,cubeB.rectangle.length
    ,cubeB.rectangle.width)
print("cubeA和cubeB的底边长方形同样独立存在")</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">wildwolf</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;wildwolf</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;wil***lf12@qq.com</p></div></span>4年前 (2019-02-28)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-41857"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;小糊涂仙</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;128***0653@qq.com</p></div><div id="runoobvote-id-41857" data-commid = "41857" class="upvotejs"><a class="upvote"></a> <span class="count">8</span></div></div><div class="comt-main" id="div-comment-41857"><p>我的实测结果与作者的理论有出入，先创建多个对象，然后再依次输出，会发现结果都是最后一个对象的值。</p>

<p>Rectangle 的封装:</p>

<pre>Rectangle = {area = 0, length = 0, breadth = 0}

function Rectangle:new (o,length,breadth)
  o = o or {}
  setmetatable(o, self)
  self.__index = self
  self.length = length or 0
  self.breadth = breadth or 0
  self.area = length*breadth;
  return o
end

function Rectangle:printArea ()
  print("矩形面积为 ",self.area)
end
-- 创建

local r = Rectangle:new(nil, 2, 3);
local p = Rectangle:new(nil, 4, 5);

-- 输出

r:printArea();
p:printArea();</pre>
<p>结果:</p>

<pre>矩形面积为     20
矩形面积为     20</pre>
<p>也就是说，p 和 r 其实不是两个完全无关的对象。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">小糊涂仙</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;小糊涂仙</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;128***0653@qq.com</p></div></span>4年前 (2019-04-15)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-42187"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;sgjz1973</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;163***2445@qq.com</p></div><div id="runoobvote-id-42187" data-commid = "42187" class="upvotejs"><a class="upvote"></a> <span class="count">7</span></div></div><div class="comt-main" id="div-comment-42187"><p>回楼上，两个新建实例并没有关系，只是新建实例时修改了元表，第二次新建覆盖了值:</p>

<pre>local Rect = {area = 0,length = 0,windth = 0};
function Rect:new(length,windth)
  local t = {};
  setmetatable(t,self);
  self.__index = self;
  t.length = length;
  t.windth = windth;
  t.area = t.length * t.windth;
  return t;
end

function Rect:ShowArea()
    print(self.area);
end

local a = Rect:new(1,2);
local b = Rect:new(3,4);
a:ShowArea();
b:ShowArea();
print(a);    
print(b);</pre>

<p>输出结果:</p>

<pre>2
12
table: 0000000019AA22A0
table: 0000000019AA2610</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">sgjz1973</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;sgjz1973</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;163***2445@qq.com</p></div></span>4年前 (2019-04-25)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-54738"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;dalige</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;459***786@qq.com</p></div><div id="runoobvote-id-54738" data-commid = "54738" class="upvotejs"><a class="upvote"></a> <span class="count">6</span></div></div><div class="comt-main" id="div-comment-54738"><p><strong>对楼上补充说明：</strong></p><p>

Rect 作为 new 出来的表(楼上代码写的 a 和 b)的元表：由于没有设置 __newindex 元方法。所以 a 和 b 在赋值的时候把长和宽的值赋给了自己，并没有把值赋给 Rect (也就是说 Rect 表中的数据一直都没有改变过)。</p>
<p>
a 和 b 在调用 ShowArea 方法的时候，自己的表里没有这个方法，会到元表中寻找这个方法，元表(Rect)中设置了 __index 元方法，所以能找到 ShowArea 这个方法，然后调用。(注意这里是 a 和 b 调用的 ShowArea 方法，所以 ShowArea 方法中  self  指向的是 a 和 b，而不是 Rect)。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">dalige</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;dalige</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;459***786@qq.com</p></div></span>3年前 (2020-06-23)</div></div></li><!-- #comment-## -->
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